1. Field of the Invention
The present disclosure relates to a light emitting device, a light source for illumination, and an illumination apparatus.
2. Description of the Related Art
Semiconductor light emitting elements such as light emitting diodes (LEDs) have a small size, a high efficiency, and a long life and thus have been used as a light source of various products for illumination and display, etc.
The LEDs have been used in an LED lamp as a light source for illumination, for example. The LED lamp can be a bulb-shaped LED lamp (an LED bulb) as a substitute for a bulb-shaped fluorescent lamp or an incandescent lamp, or a straight tube LED lamp as a substitute for a straight tube fluorescent lamp.
Also, the LEDs are used as an LED luminaire or the like as a substitute for a luminaire having a high directivity such as a downlight or a spotlight used in a store or the like.
In the LED lamp and the LED luminaire, the LEDs are incorporated into a unit as an LED module emitting device) that emits light of a predetermined color such as white light.
For example, the LED module used in the bulb-shaped LED lamp or the straight tube LED lamp generates white light by a blue LED chip that emits blue light and a yellow phosphor that emits fluorescence by blue light from the blue LED chip.
Such an LED module achieves a poor color rendition because the generated white light has a small reddish component. Accordingly, a method is also conceived of compensating for the reddish component by adding to the above-described LED module a red phosphor that emits fluorescence by blue light.
However, at the moment, the red phosphor has a lower energy conversion efficiency than the yellow phosphor. Thus, the LED module achieves a reduced light emission efficiency. Then, a technique has been studied of adding a red LED chip that emits red light instead of the red phosphor so as to improve the color rendition.
For example, Japanese Unexamined Patent Application Publication No. 2011-216868 discloses an LED module having a blue LED chip, a red LED chip, and a yellow phosphor. This achieves the LED module that emits white light having excellent color rendition.